Pneumatically controlled automatic pilot



May 14, 1946.

PNEUMATICALLY CONTROLLED AUTOMATIC PILOT Filed Sept. '5, 1941 FROM ATMOSPHERE so 47 4s TO SUMP IH 30 lol I 99 9| e5 1 25 l 32 e9 1 67 57 55 73 1| BI 63 a3 3 I Q? J 7 I07 U LI U INVENTOR, IMLL/AM ,4. lMATTHEWS,

W flw an ATTORN Y Patented May 14,

William a. Matthews, Valley Stream, N. Y., as-

signor to Sperry Gyroscope Company, Inc.,

Brooklyn, N. Y., a corporation of New York Application September 5, 1941, Serial No. 409,642

4 Claims.

The present invention relates to automatic pilots for dirigible craft, especially for aircraft. The present invention more specifically relates to aircraft automatic pilots of the type disclosed in U. S. Patents No. 2,210,916 and No. 2,210,917

to T, W. Kenyon and S. J. Zand, in which a is the pick-oil control member l9 which thereby rotates with vertical ring 3 about axis ll. This control member is formed as two substantially semi-cylindrical sections 2|, 23, axially displaced along shait i1, and inopposed positions, as shown in Fig. 2.

Control member I! is positioned within cylindrical chamber 25 formed inside member 21 supported on housing l. Member 21 is formed with two pairs of diametrically opposed openings or ports, 29, 30 and 3i, 32. Openings 23 and 3| 4 connect chamber 25 with chamber 33 which forms hunting and yet remains sensitive and positive acting at all times.

It is accordingly an object or the present invention to provide an anti-hunting servo system controlled from a relatively sensitive and-weak controlling object, such as a gyroscope.

It is a further object of this invention to provide an anti-hunting and damping device for use with a relay valve. 7

It is still another object of the present invention to provide an improved and readily adjustable pneumatically controlled anti-hunting and damping means for use with a pneumatically controlled relay valve controlling a hydraulic servo-motor.

The present invention is disclosed with respect to a rudder control system controlled from a directional gyro. It'will be clear that the invention could equally well be applied to any type of control system generated irom any type of direction-maintaining or control device.

Other objects and advantages of this invention will become apparent as the description proceeds.

In the drawing:

Fig. 1 showsa view, partly in section, of the system or the invention.

Fig. 2. shows a perspective view of the pick-oil control element of the system of Fig. 1.

In Fig. 1. there is shown a directional gyro having a housing I' in which is rotatably mounted a vertical gimbal ring. 3 as by bearings 5. R0- tatably supported within vertical ring 3 is, a

horizontal gimbal ring I in which is mounted the rotor housing 3, pivoted as at ii about a normally horizontal axis perpendicular to the pivot axis of horizontal ring I. The gyro rotor may be rotated in any suitable manner, such as by air, by vacuum, or electrically. A compass yielding direction indication,

Also fastened to vertical ring 3, as by shaft I1, 55

a portion of an annular cavity. In like fashion, openings 33 and 32 connect chamber with chamber 35, similar to chamber 33. Also communicating with chamber 25 is a duct 41 which connects the upper half of chamber 25 to the atmosphere. Passageways 31, 39 connect chambers 33 and 35 to ducts 4i and 33 respectively, which lead to relay valve 45.

The lower half of chamber 25 is connected to a source of low pressure. Fig. 1 shows one method of effecting this. Chamber 25 is connected to housing i by passageway 43. Housing 1 may be connected to a vacuum pump by duct 5 l This same pump may serve to rotate'the gyro rotor, if an airspun gyro is used.

Inoperation under normal conditions, sections 2! and 23 are symmetrically positioned with respect to ports'29, and 3!, 32 so that equal amounts of air pass from duct 41 to passageway 43 by way of port 23, cavity 33 and port 3i on the one hand, and port 33, cavity and port 32 on the other hand. No air will flow directly from duct 41 to passageway 43, since-the upper and lower halves of chamber 25 are separated by the control member l3. It is clear that two separate chambers and two separate control members, corresponding to sections 2| and 23, may equally well be used.

As a result ofthe above balanced condition, the pressures within cavities 33 and 35 are equal, giving aero pressure diiierential between ducts ll and. It the craft, and hence housing I which is fixed thereto, should change its heading, gyro rotor 3 would maintain fixed orientation in space so that control member I! would rotate with respect to member 21, In such a case, as is illustrated in Fig. 1, section 2l or control member I! would block one port, such as p rt 33, while opening the other port 23, whereby atmospheric pressure from duct 41 is led to cavity 33 and hence to duct I. At the same time, port 3] would be blocked, so that atmospheric pressure is main- .tainedincavity 99,andport99is!u1lycpened.

cavlw 9Iandhencednctl9,tothe loweredpressureofhousing l,bywayo!duct99. Hence apressure diiferentialisset upbetween ducts 9| and 99, which operatesvalve9l,aswill bedescrlbed.

Ifthecraftheadingischangedintheother sense, reverse action would take place. That-is, duct 99 would be connected to atmospheric pressure, and duct 9| would be connected to the vacuumpumppressureinasimiiarmanner.

It is clear that the actioniof valve 49, in response to differential in ducts ll, 99, depends on the relative orientaflon of directional gyro 9 and ports 29, 99, 9|, 92, Accordingly, to provide a course-setting means, member 91, which mimics the ports, is made rotatable in housing I. Means, such as worm wheel 99, worm l9, gearing 52 and handl 59 are provided to set member 91 relative to housing and thereby determine the course to be flown.

Relay valve 49 is pnemnatically controlled hydraulic valve. The valve has an outer body 99 and an inner bore 51. Communicating with ports 59, 9| of bore 51 is duct 99, which leads to a source oi hydraulic pressure, such as a pump.- Duct 99 connects with a central port 91 of bore 51 and leads to a sump of hydraulic fluid, from which the pump obtains its charge. Also communicatlng with bore 91 are output ports 11, 19 leading to ducts 9|, 99.

Cooperating with bore 51 and ports 99, 9| and 61 is a multiple piston having three sections 99, H, 19 on the same piston rod 19. These sections 99, 19 are so dimensioned and spaced as to provide a double-acting valve. Thus in the positions shown in Fig. 1, which is the neutral position, all ports 99, ii and 91 are blocked oil-by their respective piston sections. when piston rod 15 is moved in one direction, say to the left, theportsilandfl areuncoveredsothatoutlet port TI now communicates with pressure port 99, and outlet port 19 connects with sump port 91, thereby increasing the-pressure in duct 9| over that in duct 99.

The differential pressure between ducts 9| and 99 is applied to hydraulic servo-motor 99 .tomoveitspistonll andthereby actuate rudder or other navigation control 99.

whenpistonrodiiandsectionsll, 11,1:

movetotherighhthearereversedr "lltothelei't new" andILrespectlvelytheductsflsndflwlthbore i'ladiscentopposiiemdlthereotsupplynuidto oppositeoutersurheesoithemrtersecflcnaor lendsflandfloitheflstmvflvemember. The vsivememberisthereiorembiectedtothecontrolling diiiaentialne-m'es acting n msflandflsndsbotothepesnireof emergent-heck. 'l'intiathe pee-use (or-terse) airudderllreeetingheckthrouh motorflandvahellisbflancedbythediihb mtislairmeinductslhfl. 'nieruddan pressure is tincture enrolled i1 mesnsformarelsyeontrolvalvareedllysd ratherthanruddertasismostcommonly used.

In the system thus far described, the rudder control is responsive solely to relative displacement of craft and gyro axis, and, therefore, to deviation of the craft from set course. Such a system is inherently subject to hlmting and oscillating about the desired course. since the control signal ceases only when the craft is back to its ori al course, at which time the inertia of the craft swings it beyond the desired course, resulting in hunting. To prevent this hunting it is necessary to provide a meeting or .anticipating effect, so that a definite opposing force is present to prevent the craft from overshooting its proper heading.

The present invention overcomes this hunting by providing an additional control force derived from, but delayed with respect to, the controlling eii'ect. Thus, an additional diaphragm 99 is provided, also fastened to piston rod Ii. The opposed sidesof this diaphragm are supplied with pressure from ducts 9| and 99 by way of ducts |9|, .|99, in which are inserted throttling valves I99, I91. Ducts |9|, I99 are so connected that the eifect of diaphragm 99 opposes that of diaphragms9l, 99. However, because of valves I95, I91, the effect of any craft deviation on diaphragm 99 is delayed with respect to that on diaphragms 9|, 99. Hence, when a craft deviation occurs, diaphragms 9|, 9 operate immediately to give oppomterudder to return the craft to its set course. Diaphragm 99 is ineffective at the first instant, coming into play slightly'later, at a time delay determined by the setting of throttle valves I99, I91. The effect of diaphragm 99 is to reduce the eifective signal controlling rudder 99, so that th rudder is returned to its zero or neutral position before the craft regains its set course. In fact, at the time the craft reaches its proper course, the effect of diaphragms 9|, 99 is zero, but that of diaphragm 99 persists to give a net negative eifect, so that the rudder 99 is thrown oppositely to meet the swing of the craft and prevent overshooting of the desired course.

Diaphragnflismadesmallerinareathan 9|, 99 in order to have less eflect, since the damping action requires forces smaller 90 than the actual control forces. Also, ducts l9! and I99 are jointed through .a, throttling valve Hi. This valve provides an additional means for adjusting the effect of diaphragm 99 relative to diaphragms 9!, 99. It will be seen that 56 withv'alve I fully open, diaphragm 99 is inoperative, since no pressure differential can exist on its two faces. with valve ill closed all the way, maximum eifect is obtained. Intermediate positions of the valve M will produce intermeeo diateeiiects. Valve III has little effect onthe presume diiterential between ducts 9| and 99,

since this diil'erential ismsintained across valves "land 19!.

Promtheforegoingitwlllbeseenthatthe 99 present invention has provided simple and diet:-

tive means for anti-hunt control, applied at the -relayvalve99. 'fliisrequiresnoeonnectionto theseusitive gyro mechanism, and hence avoids any distmbanee to the gym or pick-oi! mmauwmvherem mlm.

Itwmbeobvlousthatthisdevlceisnotrestrlctediorusewith aircraft rudder eontrohssiilustratcibutmaybeusedwherever arelayomtmlvslveisneeded. Adamping iustable to meet many kinds of operating conditions, is thus provided.

As many changes could be made in the above construction and many apparently widely diilerent embodiments of this'invention could be made without departing from'the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

I claim: I

1. In an automatic pilot for controlling a control surface of a dirigible craft so as to steer a straight course without hunting and comprising a hydraulic motor operatively connected with said control surface, a relay valve for controlling the flow of fluid to said motor, means responsive to the pressure of fluid supplied to said motor for eifecting a fluid-controlling movement of said valve, a primary and a secondary differential fluid-pressure-responsive means connected with said valve for eflecting fluid-controlling operations thereof, said secondary means having less area than said primary means, a position-maintaining reference having a differential airflow pick-off thereon, means for supplying fluid to both of said pressure-responsive means from said pick oif in such manner that the secondary opposes the primary means, and means for delaying the build-up of pressure in the secondary of said pressure-responsive means.

2. In an automatic pilot for controlling a control surface of a dirigible craft so as to steer a straight course without hunting and comprising a position maintainingnreference having a dlflerential air flow pick-oil thereon, a hydraulic motor operatively connected with said control surface, a relay valve for controlling the flow of fluid to said motor, means responsive to the pressure of fluid supplied to said motor for ei fecting a fluid-controllingmovement of said valve, primary and secondary diflerential fluidpressure-responsive means connected with said valve for effecting fluid-controlling operations thereof, means for supplying fluid to both of said pressure-responsive means from said pickoil in such manner that the secondary opposes the primary, means for delaying the build-up of pressure in the secondary of said pressureresponsive means. and means for controllin the rate 'of build-up and magnitude of the differential pressure in said secondary pressureresponsive means.

3. In an automatic pilot for controlling a control surface of a dirigible craft so as to steers. straight course without hunting and comprising a hydraulic motor operatively connected with said control surface, a relay valve for controlling the flow of fluid to said motor, valve and motor being connected-in pressure repeat-back relation from said surface to said valve, said valve having a bore therein and a plurality of passages communicating with said bore, a valve member movably fltted within said bore and having means subjected to the fluid controlled thereby for effecting a fluid-controlling movement thereof, a primary and secondary :iiiferential fluid-pressure-responsive means connected with said valve member for effecting fluid-controlling operations thereof, the primary responsive means having greater area than the secondary responsive means, a position maintaining reference having a differential fluid pickoi! thereon, means for supplying fluid to both of said pressure-responsive means from said pickofi in such manner that the secondary opposes the primary, and means for delaying the buildup of pressure in one of said pressure-responsive means, whereby hunting of the craft is prevented. 1

4. A device of the character recited in claim 3 further including means for controlling the mag nitude of the pressure differential applied to one of said pressure-responsive means.

" WILLIAM A. MATTHEWS. 

